Blue sedge
Carex flacca ·
A low, slowly creeping carpet of narrow, blue-grey leaves. It tolerates sun or shade, and dry or wet soil.
- Size
- 10 in tall, 18 in wide
- Zones
- 5 to 9
- Light
- Full sun to part shade
- Flowers
- Grown for its leaves
- Pets
- Not checked
- Job in a bed
- Carpet
A bed built around blue sedge
The planner designed this bed around blue sedge when this page was made: a 12 × 6 ft (3.7 × 1.8 m) naturalistic planting in zone 6, part sun. It chose the other plants from the 708 that suit those conditions, and says below why blue sedge stands where it does.
The plants
- 1 Blue sedge × 8, blue-green leaves
- 2 Bloody cranesbill 'Max Frei' × 3, pink
- 3 White snakeroot × 3, white
- 4 Bee balm 'Jacob Cline' × 3, red
- 5 Mountain hydrangea 'Tuff Stuff' × 1, blue
- 6 Golden ragwort × 15, yellow
- 7 Grecian windflower × 12, blue
Why this plant
- The only plant grown for its leaves. Leaf lasts all season, where a flower lasts a few weeks.
- Part of the matrix. The low fabric of grasses and groundcovers that the taller plants come up through.
- Part of the bed's structure. Shrubs and grasses keep their shape when the perennials die down. So does mountain hydrangea 'Tuff Stuff'.
Why here
- On the front edge. At 10 in it frames the bed without hiding it, and it is in leaf all season. It finishes 68% of the edge.
- 8 plants in 2 runs (5 and 3). Runs of different lengths make the edge a frame, not a ruled line.
Why now
- Here for its leaves, all year. They cover the 12 weeks between early March and late November when nothing on the plan is in flower.
- The only leaves in winter. From November to March it is what there is to look at.
Planned as a naturalistic planting: low grasses and groundcovers, the matrix, make up 41% of the planted ground. The most in flower at one time is 3 kinds, from late June. Cool colours (pink and blue) with red and yellow as the warm notes, and white to calm things between them.
The planner's own design check: 12 Excellent, 4 Good, 1 Satisfactory. It flags one thing to watch: White snakeroot is highly poisonous to people and horses. White snakeroot spreads aggressively.
Open this bed in the planner Change its size, the sun or the style, move plants about, or swap one for another.
Where blue sedge goes in a border
At 10 in it belongs at the front of a bed. In the planner's ten height classes it is low (6 to 12 in).
Its job: carpet. A groundcover planted in threes and fives to cover the soil: along the front, and just behind it.
One of the most adaptable groundcovers there is: it will grow in dry shade, clay or salt spray. The blue-grey carpet makes a cool background for other plants.
- Blue groundcover for difficult places
- A lawn substitute for small areas
- Under shrubs and trees
What to plant with blue sedge
Plants recorded as good partners for it, and what each pairing does:
- Hosta: bold leaves against its fine ones; spires rising out of its mound; tall enough (18 in) to stand behind it.
- Coral bells.
- Black mondo grass: spires rising out of its mound.
Questions about blue sedge
Does blue sedge need sun or shade?
Blue sedge grows in full sun (6 or more hours of direct sun a day), part sun (4 to 6 hours of sun, including some afternoon sun) and part shade (2 to 4 hours of sun, mostly in the morning).
It wants ordinary well-drained soil, of average fertility, and little watering once settled.
What zones does blue sedge grow in?
USDA zones 5 to 9. It is hardy to zone 5, which means it survives winter nights down to about −10 °F (−23 °C).
Gardening in Canada? Use the USDA zone for your town: Canada's own zone map uses different numbers.
How far apart should blue sedge be planted?
12 in (30 cm) apart, from the middle of one plant to the middle of the next. That is a little closer than its full width of 18 in (45 cm), so a group knits into one patch.
It grows 10 in (25 cm) tall. Give it the full distance from anything taller, or it will lean out towards the light.
How many blue sedge plants do I need?
At 12 in apart, set out in staggered rows:
- 12 to fill 10 square feet (about 1 m²)
- 11 for a single row 10 ft (3 m) long
- 38 to fill a 4 × 8 ft bed on its own
In a mixed border, plant it as threes and fives, along the front and just behind it.
In the bed above, the planner used eight in two groups.
Is there a native plant like blue sedge?
Blue sedge is not native to North America. These North American natives come closest to doing its job:
- Pennsylvania sedge: the same job in a bed; 4 in narrower, not evergreen.
- Plantain-leaved pussytoes: the same job in a bed; 4 in shorter, medium leaves, not fine.
Matched the way the planner's Swap button matches plants: the same job in a bed, then size, then flowering time.
Will blue sedge spread?
It spreads sideways, by runners or roots; the risk of it taking over is moderate. Spreads by underground runners and can crowd its neighbours. Dig out the edges or divide every 2 to 3 years.
What does blue sedge look like in winter?
Blue sedge keeps its blue-green leaves all winter, so it is one of the plants that hold a bed together from November to March, when the perennials have gone.
More Carex
- Appalachian sedge Carex appalachica
- Blue sedge 'Blue Zinger' Carex flacca 'Blue Zinger'
- Bowles' golden sedge Carex elata 'Aurea'
- Bristleleaf sedge Carex eburnea
- Gray's sedge Carex grayi
- Japanese sedge 'Ice Dance' Carex morrowii 'Ice Dance'
- Leatherleaf sedge Carex buchananii
- Orange New Zealand sedge Carex testacea
- Palm sedge Carex muskingumensis
- Pennsylvania sedge Carex pensylvanica
- Sedge 'Bunny Blue' Carex laxiculmis 'Hobb' (Bunny Blue)
- Sedge 'Everest' Carex oshimensis 'Everest'
- Sedge 'Evergold' Carex oshimensis 'Evergold'
- Sedge 'Everillo' Carex oshimensis 'Everillo'
- Sedge 'Frosted Curls' Carex comans 'Frosted Curls'
- Seersucker sedge Carex plantaginea
- Tussock sedge Carex stricta
- Variegated broadleaf sedge Carex siderosticha 'Variegata'
- Variegated Japanese sedge Carex morrowii 'Variegata'
In these guides
Every fact on record
- Type
- Grass
- Size
- 10 in (25 cm) tall, 18 in (45 cm) wide
- Plant
- 12 in (30 cm) apart
- Height class
- Low (6 to 12 in)
- Place in the bed
- Front
- Flowers
- None: grown for its foliage
- Leaves
- Fine texture, evergreen; blue-green
- Shape
- Mounding, spreading
- Hardy in
- USDA zones 5 to 9
- Light
- Full sun, part sun, part shade
- Soil
- Average, well-drained
- Water
- Low
- Feeding
- None needed
Not yet checked against an outside reference: its figures rest on general horticultural knowledge. Flowering times are for zone 5: later in colder zones, earlier in warmer ones. Toxicity and spread information is a general gardening guide, not veterinary or medical advice, and invasive status varies by region. If a person or pet eats a plant, contact poison control or a vet. Check your local invasive species list before planting anything with a spread warning.